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981.
982.
Hui‐Hsu Gavin Tsai Jian‐Bin Lee Sheng‐Shiuan Tseng Xiao‐An Pan Yuan‐Ci Shih 《Proteins》2010,78(8):1909-1925
The mechanisms of interfacial folding and membrane insertion of the Alzheimer's amyloid‐β fragment Aβ(25–35) and its less toxic mutant, N27A‐Aβ(25–35) and more toxic mutant, M35A‐Aβ(25–35), are investigated using replica–exchange molecular dynamics in an implicit water‐membrane environment. This study simulates the processes of interfacial folding and membrane insertion in a spontaneous fashion to identify their general mechanisms. Aβ(25–35) and N27A‐Aβ(25–35) peptides share similar mechanisms: the peptides are first located in the membrane hydrophilic region where their C‐terminal residues form helical structures. The peptides attempt to insert themselves into the membrane hydrophobic region using the C‐terminal or central hydrophobic residues. A small portion of peptides can successfully enter the membrane's hydrophobic core, led by their C‐terminal residues, through the formation of continuous helical structures. No detectable amount of M35A‐Aβ(25–35) peptides appeared to enter the membrane's hydrophobic core. The three studied peptides share a similar helical structure for their C‐terminal five residues, and these residues mainly buried within the membrane's hydrophobic region. In contrast, their N‐terminal properties are markedly different. With respect to the Aβ(25–35), the N27A‐Aβ(25–35) forms a more structured helix and is buried deeper within the membrane, which may result in a lower degree of aggregation and a lower neurotoxicity; in contrast, the less structured and more water‐exposed M35A‐Aβ(25–35) is prone to aggregation and has a higher neurotoxicity. Understanding the mechanisms of Aβ peptide interfacial folding and membrane insertion will provide new insights into the mechanisms of neurodegradation and may give structure‐based clues for rational drug design preventing amyloid associated diseases. Proteins 2010. © 2010 Wiley‐Liss, Inc. 相似文献
983.
984.
Human amniotic epithelial cells (hAECs) are potentially one of the key players in tissue engineering due to their easy availability. The aim of the present study was to develop an optimal isolation and transportation technique, as well as to determine the immunophenotype and epithelial gene expression of hAECs. Amnion was mechanically peeled off from the chorion and digested with trypsin-ethylenediaminetetraacetic acid. The isolated hAECs were cultured in medium containing 10 ng/mL epidermal growth factor until P4. The epithelial gene expression, cell surface antigen and protein expression of hAECs were analyzed by quantitative polymerase chain reaction, flow cytometry and immunocytochemistry. hAECs were also cultured in adipogenic, osteogenic and neurogenic induction media. The best cell yield of hAECs was seen in the digestion of 15 pieces of amnion (2 × 2 cm) and isolated 30 min after digestion with trypsin. F12:Dulbecco's modified eagle medium was the best medium for short term storage at 4 °C. hAECs expressed CD9, CD44, CD73 and CD90, and negligibly expressed CD31, CD34, CD45 and CD117. After serial passage, CK3, CK19 and involucrin gene expressions were upregulated, while p63, CK1 and CK14 gene expressions were downregulated. Sustained gene expressions of integrin β1 and CK18 were observed. At initial culture, these cells might have stem-like properties. However, they differentiated after serial passage. Nonetheless, hAECs have epithelial stem cell characteristics and have the potential to differentiate into corneal epithelial cells. Further investigations are still needed to elucidate the mechanism of differentiation involved and to optimize the culture condition for long term in vitro culture. 相似文献
985.
Some strains of white rot fungi, non-lignolytic fungi and litter-decomposing basidiomycetes have been recognized as PAH degraders.
The purpose of our research was to enlarge the scope of PAH-degrading fungi and explore the huge endophytic microorganism
resource for bioremediation of PAHs. In this study, phenanthrene was used as a model PAHs compound. Nine strains of endophytic
fungi isolated from four kinds of plant from Eupharbiaceae were screened for degradation of phenanthrene. The endophytic fungus Ceratobasidum stevensii (strain B6) isolated from Bischofia polycarpam showed high degradation efficiency and was selected for further studies. Into the fungal culture, 100 mg l−1 phenanthrene was added, and after 10 days of incubation, about 89.51% of the phenanthrene was removed by strain B6. Extracellular
ligninolytic enzyme activities of strain B6 were tested. The results showed that manganese peroxidase [MnP] was the predominant
ligninolytic enzyme and that its production was greatly induced by the presence of phenanthrene. To confirm the involvement
of MnP in phenanthrene degradation, promotion and inhibition studies on MnP in different concentration level of Mn2+ and NaN3 were performed. Additionally, fungal mycelium-free and resuspended experiments were carried out. The results showed no apparent
correlation between MnP activity and phenanthrene degradation. The mycelium and fresh medium were the crucial factors affecting
the degradation of phenanthrene. To date, this is the first report on PAH degradation by Ceratobasidum stevensii. This study suggests that endophytic fungi might be a novel and important resource for microorganisms that have PAH-degrading
capabilities. 相似文献
986.
Dehui Xi Hui Yang Yu Jiang Moyun Xu Jing Shang Zhongwei Zhang Shiya Cheng Lisi Sang Honghui Lin 《Journal of Phytopathology》2010,158(4):263-269
Mixed infections of Nicotiana benthamiana plants by Tobacco necrosis virus (TNV) and Turnip crinkle virus (TCV) exhibited an interference interaction. Accumulation of TNV (+)RNA as well as capsid protein in mixed infection were considerably lower than that of singly infected plants. There were also a slight reduction in the levels of TCV (+)RNA and capsid protein in doubly infected plants, which displayed the concentration of both viruses decreased in dually infected plants. Tissue immunoblot analysis of systemic N. benthamiana leaves infected by TNV and TCV singly or doubly showed the interference between the two viruses in situ, which exhibited the decrease of both viruses in doubly infected leaves although the distribution of them did not change remarkably. These results were consistent with the hybridization analysis of viral genomic RNA and coat protein. Both cross‐protection test and mixed infection of the two viruses confirmed TCV had relatively stronger interference to the infection of TNV. Interference infection by TNV and TCV induced higher increase in the levels of cytochrome pathway respiration and alternative pathway respiration in host plants, especially the latter. Interference often occurred in different strains of one kind of virus or two different closely related viruses in one genus. Our results showed that interference could also occur in different viruses belonging to different genera. 相似文献
987.
β-Adrenergic receptors can activate extracellular signal-regulated kinases (ERKs) via different mechanisms. In this study,
we investigated the molecular mechanism of β1-adrenergic receptor (β1AR)-mediated ERK activation in African green monkey kidney
COS-7 cells. Treatment of cells with isoproterenol (ISO), a β1AR selective agonist, induced phosphorylation of ERK1/2 in a
dose-dependent manner. ISO-stimulated ERK phosphorylation was not influenced by the Gβγ inhibitor, βAR kinase carboxyl terminal
(βARKct) or by the Gi inhibitor, pertussis toxin (PTX), but it was clearly abolished via inhibition of protein kinase A (PKA)
with H89, or of mitogen-activated protein kinase kinase (MEK1) with PD98059, revealing that the Gαs subunit is involved in
ERK regulation through the PKA/MEK1 pathway. We also tested the effect of the adenylate cyclase activator forskolin on ERK
activation, and the result was identical to that of ISO stimulation. Moreover, pretreatment with the epidermal growth factor
receptor (EGFR) tyrosine kinase inhibitor AG1478 or with the Src tyrosine kinase inhibitor PP2 did not affect ERK activation.
These observations suggest a mechanism of β1AR-mediated ERK activity that involves the Gαs subunit, but not EGFR or Src tyrosine
kinase. 相似文献
988.
989.
Li-Xia Cheng Jiang-Jiang Tang Hui Luo Xiao-Ling Jin Fang Dai Jie Yang Yi-Ping Qian Xiu-Zhuang Li Bo Zhou 《Bioorganic & medicinal chemistry letters》2010,20(8):2417-2420
Eight hydroxyl-substituted Schiff bases with the different number and position of hydroxyl group on the two asymmetric aromatic rings (A and B rings) were prepared by the reaction between the corresponding aromatic aldehyde and aniline. Their antioxidant effects against the stable galvinoxyl radical (GO) in ethyl acetate and methanol, and 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH)-induced DNA strand breakage, and their antiproliferative effects on human hepatoma HepG2 cells, were investigated. Structure–activity relationship analysis demonstrates that o-dihydroxyl groups on the aromatic A ring and 4-hydroxyl group attached to the aromatic B ring contribute critically to the antioxidant and antiproliferative activities. 相似文献
990.